Stone of the Week - Celestine or Celestite

This is one of my favorite minerals and I love to collect it so much, hardly a gem show passes that I don’t buy a new specimen of it each year! The official name of this mineral is celestine, however it is still commonly called celestite, and is named from the Greek word "cœlestis", meaning for celestial due to its pretty pale blue color. Celestine is made up of strontium sulfate, or SrSO4, and is similar enough to another mineral, barite (BaSO4), that these are sometimes misidentified. This mineral commonly forms in sedimentary environments.

The pretty blue celestine crystals are a favorite among collectors.


Celestine comes in a variety of colors, including colorless, white, yellow, orange, gray, green, brown, and pale blue. It is the pale blue that is most commonly sold both as specimens and as beads. The introduction of celestine in the jewelry market is fairly recent, and can make for some beautiful jewelry. However, care must be taken as it is a soft stone, and can more easily be scratched than harder minerals such as quartz. It is also very slightly soluble (dissolves) in water, so do not expose it to water or moisture for any extended period of time. It is also best not to expose it to the Sun for extended periods if you do not wish the colors to fade.


These blue celestine crystals occur with white aragonite and a few purple fluorite crystals.


The worlds largest geode, located at Crystal Cave, Ohio (refer to previous article on geodes), is made of celestine. It is 35 feet at its widest point, and has crystals as wide as 18 inches across, estimated to weigh 300 lbs. Also of interesting note, there is a micro-organism called Acantharea (radiolarian protozoans) which have skeletons of strontium sulfate (aka Celestine). Celestine has sometimes been mined as a source of strontium, but always in very small quantities.


Crystal Cave, the worlds largest geode, is made up of large celestine crystals.



If there's a stone you would like to know more about - drop me a line! Have a mystery stone? Feel free to post a comment about it, including a link to a picture, and it could be featured on this blog!


Celestine Facts:
Chemical composition: SrSO4
Color: colorless, white, yellow, orange, gray, green, brown, pale blue
Habit: prismatic and tabular, also massive and granular
Fracture: uneven
Cleavage: prismatic and basal
Luster: vitreous
Hardness: 3-3.5
Specific Gravity: 3.9
Streak: White
Occurrence: Worldwide, mainly in the northern US, Europe, and Madagascar


References

Rocks, Minerals, & Fossils of the World by C. Pellant and R. Phillips. Published 1990 by Little, Brown and Co. ISBN: 0316697966

Mindat – Celestine. http://www.mindat.org/min-927.html

Wikipedia – Celestine. http://en.wikipedia.org/wiki/Celestine_(mineral)

Wikipedia – Crystal Cave. http://en.wikipedia.org/wiki/Crystal_Cave_%28Ohio%29